JPH0745527B2 - Method for producing monodisperse vinyl polymer fine particles - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing monodisperse vinyl polymer fine particles,
In particular, it relates to a method for producing monodisperse vinyl polymer fine particles having a relatively large particle size and a uniform particle size.

Conventional technology Conventionally, according to solution polymerization using an organic solvent, a particle size of 0.5 to 1
Although it is possible to produce monodisperse particles of 00 μm, the use of an organic solvent poses a problem in safety and economy of work. Since it is only possible, it is difficult to control the polymerization reaction, and it is also difficult to control the molecular weight.
On the other hand, by emulsion polymerization, a monodisperse latex having a uniform particle size can be obtained, but the maximum particle size is generally
It was about 0.5 μm. Conventionally, as a means for increasing the particle size of polymer fine particles obtained by emulsion polymerization,
It is known that (1) reduce the amount of emulsifier, (2) reduce the amount of polymerization initiator, and (3) add an inorganic electrolyte. These methods have the drawbacks that the emulsion polymerization stability is reduced, and even if polymer fine particles having a large particle size are obtained, the particle size is polydispersed. As means for improving these drawbacks, for example, as described in JP-A-59-22904,
A method of controlling the concentration of the inorganic electrolyte, or a method of obtaining a latex of a styrene-acrylamide copolymer by using a solvent in combination with water, as described in Proceedings of the Society of Polymer Science Vol. 34, has been proposed. There is. Also, a method for enlarging particles by seed polymerization has been proposed.

Problems to be Solved by the Invention However, in the above method for controlling the concentration of the inorganic electrolyte, it was not possible to obtain particles having a particle size of 1 μm or more. Further, a method of obtaining a latex of styrene-acrylamide copolymer by using a solvent in combination with water has a particle size of 1 μm.
Although the above-mentioned products can be obtained, they cannot be applied to the monomers other than styrene and acrylamide used for the polymerization and cannot be applied to various uses. Further, the method using seed polymerization requires a significantly large number of steps until monodisperse particles having a desired particle size are obtained, and the operation is complicated and the economy is poor.

In view of the above situation, the inventors of the present invention have made extensive studies on a method for producing polymer fine particles having a particle size of 1 μm or more and having an extremely narrow particle size distribution, and as a result, have completed the present invention.

Therefore, an object of the present invention is to provide a method for producing monodisperse vinyl polymer particles having a large particle size and an extremely narrow particle size distribution.

Another object of the present invention is to provide a method for easily producing polymer fine particles without being greatly restricted by the kinds of monomers used as raw materials.

Means and Actions for Solving Problems In order to increase the particle size and maintain monodispersity, the present inventors have found that the type and concentration of the polymerization initiator, the type and concentration of the electrolyte, and the polymerization temperature. Have been found to be an important factor, and as a result of intensive studies, they have found that the above objects can be achieved when polymerization is carried out under specific conditions, thus completing the present invention.

That is, the method for producing monodisperse vinyl polymer fine particles of the present invention,
In emulsion-polymerizing one or more monomers selected from the group consisting of vinyl aromatic compounds, acrylic acid esters and methacrylic acid esters, in the presence of a surfactant other than the compound represented by the following general formula (1), As a polymerization initiator,
It is characterized in that the polymerization is carried out using 10 ⁻¹ to 10 ⁻³ mol / persulfate and 10 ⁻² to 10 ⁻⁴ mol / divalent metal sulfate as an electrolyte.

(In the formula, R ₁ and ₂ may be the same or different and each represents an alkyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted cyclohexyl group, and M represents an alkali metal.) As a result, the number average particle size is 1.0 to 1
Standard deviation of 1.25 with 0.0μm and Coulter counter
It is possible to obtain monodisperse vinyl polymer fine particles having the following particle size distribution.

Hereinafter, the present invention will be described in detail.

In the present invention, the vinyl monomer used in the emulsion polymerization is one or more selected from the group consisting of vinyl aromatic compounds such as styrene, acrylic acid esters and methacrylic acid esters, and if desired, other A comonomer of, for example, acrylonitrile or methacrylonitrile may be used as a minor component.

In the present invention, the polymerization may be carried out in one step, but it may be carried out in two steps. For example, first, a method in which only styrene is polymerized, and then styrene and another vinyl monomer are added to continue the polymerization reaction, or when a hydrophilic monomer such as methyl methacrylate is used, First, a method of polymerizing styrene, 2-ethylhexyl acrylate or the like and, after the particle size / potential balance reaches equilibrium, adding methyl methacrylate and another vinyl monomer to carry out the polymerization can be employed.

The emulsion polymerization reaction is carried out in an aqueous medium containing 60% or more of water, preferably water, in the presence of a surfactant.

As described above, the surfactant used in the present invention excludes compounds represented by the following general formula (1), and includes anionic and nonionic compounds.

(In the formula, R ₁ and ₂ may be the same or different and each represents an alkyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted cyclohexyl group, and M represents an alkali metal.) For example, higher alcohol sulfuric acid ester salts such as sodium lauryl sulfate and sodium decyl sulfate; alkylaryl sulfonates such as sodium laurylbenzenesulfonate; sodium β-naphthalenesulfonate / formaldehyde condensate; dialkylsulfo such as sodium dibutylsulfosuccinate. Succinate; alkyl diphenyl ether disulfonate; polyoxyethylene alkyl ether such as polyoxyethylene lauryl ether or alkylphenyl ether; polyacrylic acid / maleic acid copolymer, vinyl acetate / maleic acid copolymer, etc. Carboxylic acids, and the like. These surfactants may be used alone or in combination of two or more. The amount of addition of these can be set arbitrarily, but especially
It is desirable to use it in the range of 0.04 to 0.80 g / dl.

In the present invention, a persulfate-based initiator is used as the polymerization initiator, and for example, potassium persulfate, ammonium persulfate and the like are most preferably used. In this case, it is necessary to use the aqueous solution in the concentration range of 10 ^-1 to 10 ^-3 mol /. If the concentration is lower than 10 ^-3 mol /, the ionic strength will be small, and only small particle size will be obtained. If the concentration is higher than 10 ^-1 mol, the polymerization rate will be too fast, making temperature control difficult. In any case, monodisperse vinyl polymer fine particles having a predetermined particle size and standard deviation cannot be obtained.

The electrolyte is not particularly limited as long as it is a divalent metal sulfate, but CuSO ₄ and FeSO ₄ are particularly preferably used.
The concentration of the electrolyte needs to be in the range of 10 ⁻² to 10 ⁻⁴ mol /. When the concentration becomes lower than 10 ^-4 mol /
When the particle size becomes smaller or becomes higher than 10 ^-2 mol / mol, the emulsion becomes unstable. In any case, when the particle size deviates from the above range, the monodisperse vinyl polymer having a predetermined number average particle size and standard deviation is obtained. Fine particles cannot be obtained.

Further, in carrying out the emulsion polymerization reaction, the ratio of vinyl monomer and water is 5/95 to 45/55 by volume ratio, preferably 10/90.
~ 35/65.

The polymerization temperature is in the range of 40 to 80 ° C, preferably 45 to 75 ° C.

Examples Hereinafter, the present invention will be described with reference to Examples.

Example 1 A 1.0 separable flask equipped with an inclined paddle type stirring blade, N ₂ inlet, monomer charging port, and temperature controller was charged with 720 g of water,
Sodium decyl sulfate (Emar 3F: Kao Corporation) 0.8
64 g, potassium persulfate (5 × 10 ⁻² mol / amount) and cuprous sulfate (CuSO ₄ ) (1.25 × 10 ⁻³ mol / amount) were added, and potassium persulfate was dissolved. styrene
160 g was added and the temperature rise was started. Polymerization was carried out at 50 ° C for 15 hours and subsequently at 65 ° C for 9 hours. When the particle size of the obtained polymer fine particles was measured by a scanning electron microscope, the average particle size d50 was 3.5 μm, and it was confirmed that a monodisperse particle aggregate was obtained. The standard deviation of the particle size distribution measured by a Coulter counter was 1.16. The weight average molecular weight of the polymer particles was 313,000, and the glass transition point was 99 ° C.

Example 2 A separable flask similar to that in Example 1 was charged with water 72
0 g, surfactant: alkyldiphenyl ether disulfonic acid (Perex SS-H: manufactured by Kao Corporation) 0.72 g, potassium persulfate (5 × 10 ^-2 mol / amount) and ferrous sulfate (FeSO ₄ ) ( 1.25 × 10 ⁻³ mol / amount), dissolve potassium persulfate, and add 160 g of styrene,
The temperature rise was started. Polymerization was performed in the same manner as in Example 1 to obtain polymer fine particles. The average particle size d50 and the standard deviation of the particle size distribution of the polymer fine particles were measured in the same manner as in Example 1, and they were 4.2 μm and 1.18, respectively. The polymer fine particles had a weight average molecular weight of 284,000 and a glass transition point of 62 ° C.

Comparative Example 1 The same procedure as in Example 2 was repeated except that potassium persulfate was used in an amount of 5 × 10 ⁻⁴ mol / mol and ferrous sulfate (FeSO ₄ ) was used in an amount of 1.25 × 10 ⁻⁵ mol / mol. Coalescent microparticles were produced. The average particle size d50 of these polymer particles was similarly determined.
The standard deviation of the particle size distribution was 0.7 μm and 1.27, respectively. The weight average molecular weight of the polymer particles was 377,000, and the glass transition point was 62.5 ° C.

Comparative Example 2 Instead of potassium persulfate in Example 2, ammonium persulfate was used in an amount of 5 × 10 ⁻¹ mol / mol, and ferrous sulfate (FeSO ₄ ) was used in an amount of 1.25 × 10 ⁻² mol / mol. The procedure was the same as in Example 2 except that the emulsion was extremely unstable and polymer aggregates were generated.
The desired polymer fine particles were not obtained.

EFFECTS OF THE INVENTION According to the present invention, the number average particle size is 1.0 by the emulsion polymerization method.
Monodisperse polymer particles having an extremely large particle size of about 10.0 μm and a narrow particle size distribution with a standard deviation of 1.25 or less can be easily obtained without requiring complicated steps.

Further, the polymer fine particles obtained by the present invention include a biological carrier, an immobilized enzyme carrier, an immunoserological diagnostic drug carrier, a drug administration carrier, an ion exchange resin, a crystal display spacer,
It can be applied to a column filler, an electrophotographic developer, a paint, and the like, and in particular, colored polymer fine particles can be used as an electrophotographic developer as they are, which is advantageous.

Claims (2)

[Claims] 1. When emulsion-polymerizing one or more monomers selected from the group consisting of a vinyl aromatic compound, an acrylic ester and a methacrylic ester, a surface active agent other than the compound represented by the following general formula (1) is used. In the presence of an agent, the polymerization is carried out using persulfate 10 ^-1 to 10 ^-3 mol / as a polymerization initiator and divalent metal sulfate 10 ^-2 to 10 ^-4 mol / as an electrolyte. A process for producing monodisperse vinyl polymer fine particles having a number average particle diameter of 1.0 to 10.0 μm. (In the formula, R ₁ and ₂ may be the same or different and each represents an alkyl group, a substituted or unsubstituted phenyl group, or a substituted or unsubstituted cyclohexyl group, and M represents an alkali metal.) 2. The method for producing monodisperse vinyl polymer fine particles according to claim 1, wherein the electrolyte is CuSO ₄ or FeSO ₄ .